Incandescent electric lamp



I l I if 40 M,/-- I t I .20 I n W 59 E 3g 7 M 17 59- July 29, 1952 w, GERO 2,605,440

INCANDESCENT ELECTRIC LAMP Filed June 4, 1951 INVENTOR 14 z, @520.

ATTORNEY I Patented July 29, 1952 [UN TED STATES PAT E 2,605,440 INCANDESCENT ELECTRIC LAMP William B. Gero, Maplewood, N. J assignor to 'Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application June 4, 1951, Serial No. 229,796

, 10 Claims. (01. 313-344) This invention relates to lamps and, more particularly, to-filaments for projection lamps.

The conventional filament for a projection lamp is a biplane ten-section filamentary electrode having the first and last sections for mounting on the stem leads, the second and third and eighth and ninth sections as outersections, and the remaining-four sections as center or inner sections.

During the operation of the projection lamp, the center and outer sections of the filament mutually receive heat from one another. The outer sides of the outer sections are, however, cooled by conduction through and convection currents in the fill gas. Hence, the center sections operate at a higher temperature than the outer sections, thereby giving both non-uniform filament temperature and resultant screen illumination. In addition, the center sections tend to develop hot spots whichcause the material of the filament to vaporize and the wire to break, thus ending the life of the lamp. Fur-1 ther, a non-uniform light source is extremely difficult to focus and decreases the resulting screen intensity.

Hence, it has been found advantageous, according to my invention, to mount refractory metal reflectors on thesupporting lead wires of the stem in close proximity to the respective outer sections of the filament for the purpose of refleeting heat back to the outside sections, thereby producing a more uniformly heated filament.

In its general aspect, the present invention has the object of overcoming the afore-mentioned disadvantages of the prior art filaments for hotaspots inthe center section and will give a longer lamp life.

A further object is a biplane continuous coil sectional filament for a projection lamp and refractory metal reflectors mounted on the lead wires of the stem in close proximity to the outer sections of the filament to reflect heat back to the outer sections, thereby producing a more uniformly heated filament.

2 V 7 Other objects and advantages of the invention' will appear to those skilled in. the art to which it appertains as the description proceeds, both by direct recitation thereof and by implication from the context.

Referring to the accompanying drawing, 'in which like numerals of reference indicate similar parts throughout: I

Fig. 1 is an elevational view of a projection lamp embodying'my invention; i Fig. 2 is a transverse sectional view of the lamp of Fig. 1, in the direction of the arrows, along line IIII; L Fig. 3 is a fragmentray sectional view, similar to Fig. 2, but enlarged to show details. of

my invention. Referring to the drawing in detail, the reference numeral ll designates an incandescent electric lamp, such as a projection lamp manu-v iactured for base-down operation, and compris; ing a vitreous envelope or bulb l2 with an opaque end section, a base l3, and enclosing a mount M.

This mount l4 comprises a stem l5, leadi-ngin and supporting conductors I6 and H extending through the press l8 of stem IS, a top fixed bridge IS, a bottom floatingv bridge 20, filament leg inserts 2|, and a filament 22. The stem I5 is sealed to the bulb and provided with an exhaust tube opening'therethrough, as indicated at 23. Leading-in conductors l6 and ll are bent at right angles outwardly from the axis of the stem a short distance. above the press and then vertically upward or parallel to the bulb axis. The upper or free extremities are bent inwardly at right angles and terminate close to the axis of the stem. Connected to the free end portions of conductors l6 and H by means of outer support wires 24, is a fixed top insulating bridge l9. This bridge I!) consists of a piece of vitreous cane having embedded therein the upper extremities of wires 24 and of top filament sup port Wires 25. These wires 25 of bridge lfljde pend from said bridge and support filament 22 by means of ahook formed in the lower ends of said wires 25. This biplane sectional filament 22 comprises, in the present embodiment as shown in Fig.3, ten sections, namely fragmentary terminal sec-' tions 26 and 21, outer sections'28, 29, 30 and 3| and center or inner sections 32 and 33, 34, 35 These sections are connected by inter-section loops and staggered, so that five are disposed i n' one normally vertical plane parallel, to that of leading-in conductors l6 and I'l and'five in a normally vertical plane parallel theretoand so spaced that in plan they'lie at the vertices: of I by welding, to the free end of leading-in conduc tors l6 and I1.

For the purpose of positioning filament .22 between conductors l6 and H, a floating bottom bridge 20 is provided, free to slide on the lower portions of leading-in conductors I6 and I! by means of side guide wires 36. This bridge 20 is similar in construction to bridge [9, except that :in the presentshowingthereare four lower filament support wires r3! for engaging the lower uficoiled inter-section portions offilament 22 by means .of their. hooked upper extremities. Depending from the vitreous cane portion of bridgev 13.6, is a bottom guide wire 38 which is free to slide within the outer loop oiaspud or'dummy lead 39 projecting from press I9,

According to my 'inventionheat reflectors 40, one suitably secured tolthe, inner side of each of theJleading-in conductors Wand, ll, as by welding, and'symmetrically placed about the outer sections of filament 22, are providedto reflect, for example, as shown in Fig. 3,radiated heat from section 29 into section 38 and vice versa.

- Some heat is radiated frcm and absorbed in the terminal sections as, vfor example, section 126. reflectors, suitably formed of refractory metal such as molybdenum, are portionsof a cylindrical mirror'havingits center of curvature along the axis of the filament and midway between-the centers of the next adjacent outer section's,-'such as sections 28 and 29 of filament .22. A-'-mi-rror-like surface is provided on-the inside oi refle'ctors 40 by electropolishing them in any desired-manner, as by means of a chemical solution. It will be understood that the 'refiectors 40 may be made of a non-metallic material, such as a ceramic or plastic, suitably coated on the inner reflecting surface at least with a metal such-as silver. a

Thus it will be seen from the foregoing'description that my invention has overcome the aforementioned disadvantages of the prior art filaments for projection lamps. I have provided a biplane sectional filament 22 for an incandescent electric lamp,such as projection lamp H, with refractory metal reflectors 49 mounted on the leadm'g in conductors l6 and H of the stem If: in spaced proximity to 'adj'acent outer sections, such as sections '29 and 30 of said filament, to reflect the heat from said outer sections and thereby return it to said outer sections. This produces a substantially uniformly heated filament for a projection ,lamp which will increase screen intensity and uniformity, "and facilitate focusingonthe screen. Y

"'While a preferred embodiment ofmy invention has been disclosed, it will be understood that modifications may be made within thespirit and scope of the appended claims.

;I=claim:

1. An incandescent electric lamp comprising an enclosing envelope. and mount; said mount consisting of a stemhaving extending therefrom leading-in and supporting conductors and a dummy lead with a loop on its free end, a fixed top insulated bridge for connecting the free end portions of said conductor supports depending from said bridge, a filament having a plurality of coiled sections comprising terminal sections, outer sections and center sections united by looped portions and connected to said supports, filament leg inserts connected to said terminal sections and said conductors, a bottom floatin bridge supported by and below said filament and slidable on .said conductors and in said loop of said dummy lead, and a reflector mounted on each of said conductors in spaced proximity to adjacent terminal sections of said filament.

2. An incandescent electric lamp comprising an enclosing envelope and a mount; said mount consisting of a stem having extending therefrom leading-in and supporting conductors and a dummy lead with a loop on its free end, a fixed top insulated bridge for connecting the free end portions of said conductor, supports depending from said bridge, a filament having a plurality of coiled sections comprising terminal sections, outer sections, and center sections united by looped portions and connected to said supports, filament leg inserts connected to said terminal sections and said conductors, a bottom floating bridge supported by and below said filament and slidable, on said conductors and in said loop of said dummylead, and a refractory metal -reflector mounted on each of said conductors in spaced proximity to adjacent terminal sections :onsaid filament.

3. An incandescent electric lamp comprising anenclosing envelope'and a mount; said mount consisting ofa stem having extending therefrom leading-in and supporting conductors and a dummy lead with a loop on its free end, a fixed top insulated bridge for connecting the freeend portions of said conductor supports depending from said bridge, a filament having .a plurality of coiled sections comprising terminal sections, outer sections and center sections vunited'by looped-portions and connected to said supports, filamentleg inserts connected to said terminal sections :and said conductors, a bottom floating bridge supportedby and below saidfilament and slidably on saidconductors and insaid loop of said dummy lead, and a reflector mounted on each of said conductors in spaced proximity to adjacent terminal sections of said filament.

4. A mount for an incandescent electric lamp comprising an enclosing envelope and a mount; said mount consisting-of-a stem having extending therefrom leading-in and supportingconductors and a dummy lead with -a loop on its free end, a fixed top insulated bridge for connecting the free end portions of said conductor supportsdepending from said bridge, a filament having a plurality of coiled sections comprising terminal sectionsouter sections and center sections-united by looped portions and connected to said -'supports, filament leg inserts connected tosaid-terminal sections and said conductors, -a bottom floating bridge supported byandbelowsaL-i-d filamentand slidable on said conductors and in said loop of said dummy lead, and a reflector mounted on each of said conductors spaced proximity to adjacent terminal sections of said filament.

5. A mount foran in'candescen-t electric lamp comprising an enclosing envelopeand a mount; said mount consisting of astem having extending therefrom leading-in and supporting conductors and a dummy lead with aloop'on itsfre'e end, a fixed top insulated bridge for connecting the free end portions of said conductor supports depending from said bridge, a filament having a plurality of coiled sections comprising terminal sections, outer sections and center sections united by looped portions and connected to said supports, filament leg inserts connected to said terminal sections and said conductors, a bottom floating bridge supported by and below said filament and slidably on said conductors and in said loop of said dummy lead, and a refractory meta-l reflector mounted on each of said conductors in spaced proximity to adjacent terminal sections of said filament. 1

6. A mount for an incandescent electric lamp comprising an enclosing envelope and a mount; said mount consisting of a stem having extending therefrom leading-in and supporting conductors and a dummyvlead with a loop on its free end, a fixed top insulated bridge for connecting the free end portions of said conductor supports depending from said bridge, a filament having a plurality of coiled sections comprising terminal sections, outer sections and center sections united by looped portions and connected to said supports, filament leg inserts connected to said terminal sections and said conductors, a bottom floating bridge supported by and below said filament andslidably on said conductors and in said loop of said dummy lead, and a cylindrical reflector mounted on each of said conductors in spaced proximity to adjacent terminal section of said filament.

7. In combination with a biplane sectional filament for an incandescent lamp, a reflector mounted in spaced proximity to the outer sections of said filament.

8. In combination with a biplanesectional filament for an incandescent electric lamp, a re- 10. In combination with a biplane sectional filament for an incandescent lamp, a cylindrical mirror reflector having its center of curvature along the axis of said centers of the next adjacentouter sections of said filament.

WILLIAM B. 'GERO.

No references cited. 

